Chemical conversions employing solid catalysts are often conducted using a fixed or fluidized bed of catalyst particles. That is, the material to be converted is contacted with a solid catalyst present in a fixed bed of particles or in a fluidized bed of particles. However, each of these two modes of operation has serious disadvantages. For example, the use of a fixed catalyst bed often results in temperature control problems which adversely affect catalyst performance. Regeneration and/or reactivation of a fixed catalyst bed can result in substantial process downtime since the chemical conversion must be stopped in order to safely treat the catalyst, e.g., while the catalyst remains in the reactor vessel. Obtaining a uniform catalyst activity distribution is also difficult with fixed catalyst beds, in particular, in situations where frequent regenerations are required.
Fluidized catalyst beds do, in general, provide better temperature control than do fixed catalyst beds. However, fluidized catalyst bed reaction systems can be much more complex than fixed catalyst bed reaction systems. For example, fluidized catalyst bed reaction systems usually involve at least two separate vessels each containing a fluidized catalyst bed, one in which to conduct the chemical conversion and one in which to regenerate the catalyst. Catalyst particles are transferred, e.g., substantially continuously transferred, between the two separate vessels. Separation devices, e.g., cyclone separators and slide valve assemblies, are often needed in both vessels to separate the catalyst particles from the feedstock/reaction product and the regeneration medium and to control the flow of catalyst between the two vessels. Such devices tend to produce increased catalyst losses through particle attrition since particle velocities within these separators are often rather high.
"Hydrocarbons from Methanol" by Clarence D. Chang, published by Marcel Dekker, Inc. N.Y. (1983) presents a survey and summary cf the technology described by its title. Chang discusses methanol to olefin conversion in the presence of molecular sieves at pages 21-26. The examples given by Chang as suitable molecular sieves for converting methanol to olefins are chabazite, erionite, and synthetic zeolite ZK-5.
Catalysts comprising one or more crystalline microporous three dimensional materials or CMSMs include naturally occuring molecular sieves and synthetic molecular sieves, together referred at as "molecular sieves," and layered clays.
Among the CMSMs that can be used to promote converting methanol to olefins are non-zeolitic molecular sieves or NZMSs, such as aluminophosphates or ALPOs, in particular silicoaluminophosphates or SAPOs disclosed in U.S. Pat. No. 4,440,871. U.S. Pat. No. 4,499,327, issued Feb. 12, 1985, discloses processes for catalytically converting methanol to light olefins using SAPOs at effective process conditions. U.S. Pat. No. 4,861,938, issued Aug. 29, 1989 discloses a process for catalytically converting a feedstock containing 1 to about 6 carbon atoms per molecule into a product wherein the catalyst is regenerated and thereafter conditioned in order to have increased effectiveness during the conversion stop. U.S. Pat. No. 4,873,390, issued Oct. 10, 1989 discloses a process for catalytically converting a feedstock into a product wherein carbonaceous material is deposited on the catalyst during the conversion and thereafter the catalyst is regenerated at conditions effective to remove only a portion of the carbonaceous material from the catalyst. U.S. Pat. No. 4,814,541, issued Mar. 21, 1989, discloses a process for catalytically converting a feedstock into product using a solid catalyst that is present in a slurry with a liquid other than the feedstock or product.